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At 06:16 PM 10/23/99 +0100, Mark Dixon wrote:

[SNIP]

>3)    On a long hang with the cave reel I find it best to clip the locked
off reel to my top D-ring and just float along at 6m while neutrally
buoyant.  This takes any tension off your arm Only risk here is getting
scooped up by a passing ship.  Lets just hope that those topside would deal
with this.

[SNIP]

I would *never* do this.

Deco should *always* be done in a horizontal position.  Since
the lungs are elongated along the length of the chest, this
position most evenly distributes the pressure differential
between the top and bottom of the lungs as well as between the
the head and feet.  This is important because decompression
calculations are done using a single theoretical point-location
in the water column.  If you're "hanging" vertically in the
water, the pressure difference between your feet and head (as
well as between the top and bottom of your lungs) can be significant.
This is especially so near the surface where the pressure gradient
is very steep.  That's to say that a one-foot error in your stop
at your ten-foot stop is a 10% error (pretty significant).  The
same one-foot error at 100 feet is only a 1% error (not as
significant).  Precise depth control during deco is important at
all depths, but near the surface it's critical.  This is why the
difference in the depth of your feet vs your head makes it
important to remain horizontal during deco.

Additionally, if a boat a fisherman's hook (this happened to me
once) snags your lift-bag, it may pull you to the surface before
you can release the reel.  If the pull is strong enough, it may
make it difficult or impossible to unclip the reel against the
tension.

If you're having trouble staying horizontal during deco, you
may be able to solve the problem by spending some time a in
pool adjusting your trim.

-Mike Rodriguez
<mikey@ma*.co*>
Pn(x) = (1/(2^n)n!)[d/dx]^n(x^2 - 1)^n

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